When adding "hosts allow = 192.168.1." in [global] section of smb.conf, samba server takes 6 seconds before accepting the connexion from any host. I need to wait 6 seconds when typing smb://192.168.1.100/x in nautilus (or \\192.168.1.100\x in windows) before I'm asked for the username and password.
"hosts allow" is added in smb.conf when using gsambad 0.2.7 to choose which IP address can access the share.
Using samba 2:3.2.3-1ubuntu3 in ubuntu 8.10 :

Mmh, I'm not sure that I would have necessary skill to do this, unless there is some tutorial to help me giving you the necessary information.
I also found that changing "hosts allow = 192.168.1." to "hosts allow = 192.168.1.100" removes the timeout problem. The same apply if you use another IP, 127.0.0. and 127.0.0.1 for localhost, as an example. I tested this on one machine and one virtual machine.